Field of the Invention
The present invention relates to a process for producing corrosion-resistant ceramic members. More particularly, the invention relates to a process for producing corrosion-resistant ceramic members, which are to be favorably used as members in semiconductor-producing apparatuses such as heat CVD apparatuses.
With the increase in memory capacity of super LSIs, the degree of fine processing of such super LSIs has been increasing greatly, and processes requiring chemical reactions have been expanded. Particularly, in the semiconductor-producing apparatuses requiring a super clean state, a halogen-based corrosive gas, such as a chlorine-based gas or a fluorine-based gas, is used as a deposition gas, an etching gas or a cleaning gas.
In a heating apparatus-in which a semiconductor is heated while being contacted with such a corrosive gas, for example, a semiconductor-producing apparatus such as a heat CVD apparatus, a semiconductor-cleaning gas composed of a halogen-based corrosive gas such as ClF.sub.3, NF.sub.3, CF.sub.4, HF or HCl is used after the deposition. In the depositing step, another halogen-based corrosive gas such as WF.sub.5 or SiH.sub.2 Cl.sub.2 is used as a film-forming gas.
Each of the members constituting the semiconductor-producing apparatus is made of alumina or aluminum nitride. When such members are exposed to and contacted with the above halogen-based corrosive gases at a high temperature, their surfaces corrode and subsequently, the corroded portion peel from the members in the form of particles.
If such particles are heaped on a substrate placed in the semiconductor-producing apparatus, the heaped particles cause insufficient insulation or insufficient conductivity resulting in making the semiconductor unacceptable.
In view of the above problem, NGK Insulators, Ltd. disclosed in Japanese patent application No. 3-150,932 (filed on May 28, 1991) and Japanese patent application No. 4-58,727 (filed on Feb. 13, 1992) that a sintered body made of aluminum nitride with a layer of aluminum fluoride on the surface thereof exhibits high corrosion resistance against plasmas of the above noted halogen-based corrosive gases. That is, even when the aluminum nitride sintered body is exposed to the ClF.sub.3 gas or similar gas for one hour, the surface state of the sintered body does not change.
Further, NGK Insulators, Ltd. disclosed in JP-A 5-251,365 that a film of aluminum fluoride is formed on a surface of a sintered body made of aluminum nitride by using a gas phase growing method.
Further, it is disclosed in JP-A 7-273,053 that in order to prevent corrosion of the surface of an electrostatic chuck for semiconductor wafers, the surface is subjected to a surface treatment in which a film of aluminum fluoride is formed through preliminarily replacing the surface of the electrostatic chuck by fluorine with use of fluorine plasma.
The aluminum fluoride layer on the surface of the aluminum nitride sintered body as described in Japanese patent application No. 3-150,932 and Japanese patent application No. 4-58,727 may be formed by using the sputtering technique. However, when the sputtering technique is used, only the surface of the sintered body opposed to a sputtering target is covered with aluminum fluoride. Therefore, if the member to be covered has a cylindrical shape, it is difficult to cover a peripheral face of the member.
If the gas phase growing technique as disclosed in JP-A 5-251,365 is used, the above-mentioned problem can be prevented, because the raw gas to be subjected to a reaction is fed to a peripheral surface of a cylindrical member. Further, if the fluorine plasma is used as disclosed in JP-A 7-273,053, the above-mentioned problem can be also prevented, because the fluorine-based gas to generate the plasma is sufficiently fed to the peripheral surface of the cylindrical member.
However, in order to completely cover the member with aluminum fluoride, each of the gas phase growing reaction and the plasma processing needs to be continuously effected for 50 hours or more in these techniques. Thus, clearly, these techniques require a lengthy processing time which leads to extremely poor productivity.
Further, if the gas phase growing reaction or the plasma treatment is effected with the fluorine-based gas for a long time period, the chamber used for effecting the above reaction or treatment is also corroded, thereby increasing the costs of processing.